History of Life on Earth

Question 1

give 4 examples of INDIRECT methods to date fossils & rocks

Answer 1

1. Relative Dating
   Layers; any rock layer below this one is older -> judge ages relative to each other
2. Paleomagnetic Dating
   Particles of rock orientate towards earth’s poles ; tempo @ which magnetic poles of earth change & compare it with orientation of particles
3. Fauna Comparisons
   fossils are found in & between layers of volcanic rock that can be dated
4. Dendrochronological Comparisons
   trees annual rings -> age & climate

Question 2

Name a direct method to date rocks and fossils and explain in full

Answer 2

RADIOMETRIC DATING

• rocks contain radioactive isotopes -> uranium ; thorium ; potassium
• these isotopes decay at a constant rate
• age can be determined by: studying ratio of radioactive isotopes & their stable forms ; uranium decays to lead
• different isotopes date different rocks & materials ; mineral contents & type of fossils determine the method used
• radiometric dating measures in millions of years
• radiometric dating methods are constantly refined to get more accurate

Question 3

From the Earth’s history what is a hypothesis for how life on earth began?

Answer 3

Life probs started as an organic molecule with the ability to replicate itself ; the molecule most likely used is RNA for this replication

Question 4

what was the most primitive form of life on earth & where can they be found?

Answer 4

• a group of bacteria : Archaea / Archaeabacteria
• From hot water sources in volcanic areas / warm water spouts in the deep sea / marshy areas with little or mo oxygen or water in high salinity

Question 5

where do scientists think the earliest form of life originated from?

Answer 5

warm water spouts under the sea

Question 6

what was the group called after archaea and why were they important?

Answer 6

eubacteria ; first photosynthetic organisms as well as process of denitrification and fixation of nitrogen

Question 7

why was the development of the cyan bacteria so important? explain in full detail

Answer 7

• cyan bacteria have off oxygen as a waste product of photosynthesis so:

1. life could exist anywhere on earth
2. light energy was used
3. only ground substance was need were water & carbon dioxide -> available in abundance
4. oxygen was produced

Question 8

how does the atmosphere adapt to make life suitable? (5)

Answer 8

1. photosynthesizing bacteria take in C02 and release 02
2. concentration of C02 decreased as photosynthesizing organisms increased
3. nitrogen levels increase ; cyan bacteria used N2 in water to produce proteins
4. Atmospheric pressure decreased
5. development of the ozone ; increased O2 & increase exposure to ultraviolet

Question 9

why was there never a balance between CO2 and O2

Answer 9

• not all dead organisms decompose
• some were buried under layers of sediment to later turn into fossils
• CO2 in seawater bound with calcium to from calcium carbonate -> calcium came from erosion of rocks

Question 10

discuss how potentially eukaryotes were formed

Answer 10

archaebacteria hijacked the eubacteria

aerobic purple bacteria became the mitochondria

Question 11

discuss the potential origin of chloroplasts

Answer 11

endosymbiosis between unicellular organisms with mitochondria & photosynthetic cyan bacteria

Question 12

what is the cambric explosion?

Answer 12

when there was an abundance of fossils between 500-600 mya

Question 13

what are fossils?

Answer 13

remains of organisms that lived previously and were conserved especially in sedimentary rocks and

Question 14

how are fossils formed? explain in absolute full detail

Answer 14

1. organism dies & can be converted in sediment ( bottom of sea/river )
2. anaerobic conditions -> decomposition is possible
3. covering with sediment ; must be fast & happens bottom of sea,river/ lake
4. hard parts can be replaced by minerals
   or
5. dissolve & only leave an impression of natural form
   or
6. impression can be filled with minerals leaving a mould
   or
7. whole organisms can be kept intact -> resin

Question 15

what types of fossils can be found?

Answer 15

1. Body fossils -> skeletons/bones
2. Form fossils -> sediment gardens around organism but organism is dissolved by acid water
3. Moulds -> cavity filled with minerals
4. Trace fossils -> marks made by animals as it walked over sediment that hardened
5. Unchanged fossils -> insects in resin / frozen fossils ; mummified in dry temps

Question 16

what percentage of organisms became fossils?

Answer 16

0.1%

Question 17

name an example of a transition fossil and why it’s so important

Answer 17

Archaeopteryx

exhibits fine reptilian as well as avian features

Question 18

why are fossils so important? what can we deduce from them?

Answer 18

• trends in biodiversity
• evolutionary relationships
• forming of sediments & enabling us to understand environmental changes
• explore for economically important minerals

Question 19

how is coal formed?

Answer 19

1. often happens in marshy areas ; layer of organic material turns into peat
2. rivers flood and peat is covered with sand ( sediment )
3. slowly subjected to higher pressures
4. all oxygen & hydrogen disappear from layers and carbon increases then peat turns into coal

Question 20

what were the transition animals for mammal-like reptiles called?

Answer 20

terapsids

Question 21

why do 99,9% of species go extinct?

name 5 reasons

Answer 21

• couldn’t adapt to changing climate
• didn’t have time to adapt
• other species developed into new species
• new species were better competitions and existing species couldn’t survive
• killed by whatever causes extinction e.g. meteorite

Question 22

define extinction

Answer 22

massive number of species all over the world die simultaneously

Question 23

what is the sixth extinction and how is it different from other extinctions?
Also what caused it

Answer 23

• the damage done by man
• caused by man & much faster
• result of exploitation of natural resources, habitat destruction and pollution

Question 24

name 3 intrinsic factors that caused mass extinction on earth

Answer 24

• volcanic eruptions
• continental drift
• ice ages

Question 25

name the effects of volcanic eruption on earth

Answer 25

1. ash & dust blocked sun rays
   • cooling down of earth
   • photosynthesis couldn’t happen = collapse in food webs
2. SO2 fell as acid rain
3. CO2 causes greenhouse effect & global warming increased
   • temp of earth increased
   • ocean currents didn’t flow as before
   • nutrients wasn’t circulated anymore

Question 26

name 3 things continental drift possible led to

Answer 26

• increased competition between species
• changes in abiotic conditions
• increased volcanic activity

Question 27

what is one of the most important effects of an ice age?

Answer 27

it’s DRIER
much less available water
leads to large scale of habitat changes

Question 28

name 2 other effects of an ice age

Answer 28

1. lower sea levels
   • habitats of marine animals decreased
   • marine animals couldn’t adapt to increased salinity & O2 levels
2. species were forced to migrate northwards towards the equator
   • competed with tropical species
3. obvi less water

Question 29

name an extrinsic factor of mass extinction

Answer 29

meteorite collisions

Question 30

discuss in FULL what happens when a meteorite hits the earth

Answer 30

• dust, sand etc block sun rays ; photosynthesis can’t take place -> food chains = 😵
• sulphuric acids forms acid rain
• blocking sunlight = cool down of earth
• low temps = not right for dinos who couldn’t control body temp
• gaseous exchange -> availability of O2 if affected
• Fires spread

Question 31

is there evidence for the meteorite collision theory? ( The big bang )

Answer 31

• large amounts of iridium in rock layers ( abundant in meteorites but not in rocks )
• shock quartz formed in conditions of extreme heat -> found in rock layers
• impact crater

Question 32

what’s the largest and oldest impact crater?

Answer 32

Vredefort dome